I have a 2008 Frontier crew, when ever i turn the AC unit or the heating system on I have a very loud noise that comes from under the hood. It sounds like a loud cranking that comes and goes reapeatly. Something on the lines of the bearings are going out in something. Im not sure. Does anyone else have any experience with this. Any advice or input is greatly appreciated. Thank you in advance for your help.

I have a 2008 Frontier crew, when ever i turn the AC unit or the heating system on I have a very loud noise that comes from under the hood. It sounds like a loud cranking that comes and goes reapeatly. Something on the lines of the bearings are going out in something. Im not sure. Does anyone else have any experience with this. Any advice or input is greatly appreciated. Thank you in advance for your help.